Blind source separation of multichannel neuromagnetic responses

Magnetoencephalography (MEG) is a functional brain imaging technique with m illisecond temporal resolution and millimeter spatial sensitivity. The high temporal resolution of MEG compared to fMRI and PET (milliseconds vs. seco nds and tens of seconds) makes it ideal for measuring the precise time of n euronal responses, thereby offering a powerful tool for studying temporal d ynamics. We applied blind-source separation (BSS) to continuous 122-channel human magnetoencephalographic data from two subjects and five tasks. We de monstrate that without using any domain-specific knowledge and without maki ng the common assumption of single- or multiple-current dipole sources, BSS is capable of separating non-neuronal noise sources from neuronal response s and also of separating neuronal responses from different sensory modaliti es, and from different processing stages within a given modality. (C) 2000 Elsevier Science B.V. All rights reserved.